1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device in which, for fine patterning, pattern transfer is performed such that an original pattern mold (template) having formed thereon a pattern to be transferred is brought into contact with a substrate to be transferred such as a wafer or the template and the substrate to be transferred are brought close to each other.
2. Description of the Related Art
In methods of manufacturing semiconductor devices, a nanoimprint method in which an original pattern mold is transferred to a substrate to be transferred is attracting attention. The nanoimprint method can achieve both the formation of a fine pattern of 100 nm or less and mass productivity.
The nanoimprint method is a method in which a patterned template is pressed against a resist layer made of an imprint material applied onto a substrate to be transferred and the resist layer is cured, whereby a pattern is transferred to the resist layer. As the nanoimprint method, mainly, a thermal imprint method using a thermoplastic resist and a photo-imprint method using a photocuring resist are known (see, for example, Jpn. Pat. Appln. KOKAI Publication Nos. 2001-68411 and 2000-194142).
By the nanoimprint methods, a pattern of a three-dimensional structure formed on a template can be transferred onto a substrate to be transferred. Hence, a pattern of, for example, a step structure or a lens form can also be transferred onto a substrate to be transferred.
The procedural steps of pattern transfer by a photo-nanoimprint method which is one type of nanoimprint method include, for example, the following (1) to (5):
(1) Apply a photocuring resist which is an imprint material to a substrate to be transferred;
(2) Align and press (bring into contact) the substrate to be transferred and a template;
(3) Cure the resist by light irradiation;
(4) Mold release and rinse; and
(5) Remove remaining films using anisotropic etching mainly by oxygen plasma.
For the application method of a photocuring resist which is an imprint material to a wafer, a spin coat method and an inkjet method are used.
The spin coat method enables to improve throughput. In the spin coat method, however, since an imprint material is a liquid, handling is difficult up to the point of light irradiation. In addition, the use efficiency of an imprint material is poor.
On the other hand, in the inkjet method, steps up to mold release can be performed in an imprint apparatus. Thus, a wafer having a liquid imprint material applied thereto does not have to be moved between manufacturing apparatuses. Hence, the inkjet method is less susceptible to liquid level change, etc. Only one shot (one press by a template) of an imprint material is applied. Thus, the use efficiency of an imprint material is high. However, in application of an imprint material, the amount of discharge needs to be controlled on the order of picoliters. Thus, there is a need to read an amount of discharge from mask pattern data to create a discharge pattern of an imprint material according to the density of a pattern, and control the amount of discharge.
A template used in the photo-nanoimprint method is, for example, a fully transparent quartz substrate which is used for general photomasks, on which a pattern of projections and recesses is formed by plasma etching. Taking a pattern layout of memory devices as an example, a memory cell pattern formed by lines and spaces is formed at a central portion of each chip. Outside the memory cell pattern is formed a peripheral circuit pattern. Furthermore, outside the peripheral circuit pattern is arranged a dicing region serving as a cutting margin portion of the chips. In the dicing region are formed alignment marks for alignment, etc.
Meanwhile, there is a large pattern where a resist of several hundred micrometers or more remains over the peripheral circuit portion and the dicing region. In a large pattern where a resist thus remains over a wide region, the capillary force decreases and thus the filling speed of an imprint material decreases. This causes problems that manufacturing time increases and filling with an imprint material is not sufficient, resulting in a partial loss of a pattern.